A hallucination is the perception of a stimulus that is not actually there. It's something that makes you aware of its existence but is not real -it does not belong to the physical world. Some examples of hallucinations are a desert mirage, or a sound we "might" have heard, but no one else in the room noticed. The reason why hallucinations can be very disorienting and unpleasant is that our minds and bodies are constantly interpreting the environment around us, in search for cues, details and information.

When we perceive something about the world outside of us, we automatically ask questions like: is it going to hurt, pose a threat to my life, or be pleasant? Is it a familiar sight or a newly encountered object? Hallucinations trick the mind because they seem as real, but they represent things that are not there, so that our mind has a different reading of the situation. The line between sanity and "mental disorders" is very thin, oftentimes defined by a society's beliefs and interests at a certain point in history. Proof of that is the fact that hallucinations, should they be of a visual or auditory kind, can occur both in healthy and sick individuals. They reflect a particular state that our organism is going through or a more permanent situation ... in which case we define the individual as "mentally disturbed".

A series of situations, such as sleep deprivation and temporal lobe epilepsy, can cause hallucinatory experiences. People affected by schizophrenia -the kind with "positive" symptoms- will also have hallucinations. Positive symptoms of schizophrenia are the kind of things a person will do which are noticeable because obviously "out of place", therefore a person affected by the disorder and its positive symptoms will have disordered thoughts, hallucinations and delusions (a delusion is believing something that in reality is not true). What all these individuals have in common is the special combination of chemicals in their brain, which causes them to see and hear things that are not there.

It has been said that hallucinations are closely related to dreams, because of the way that they are "lived" and therefore understood at a very deep and personal level. At the base of both dreaming and hallucinating lies the fact that what we see and hear deceives our senses ... not reflecting something that is actually happening, but being very real all the same. When hallucinations and dreams trick our senses, we are living a passive experience. That means that we did not choose to dream a specific Fairy Land, but we just happened to be right in the middle of it, with little ability to change the course of things. The person has no control over the hallucinations either. True, it is possible for almost everyone to cultivate the ability of "lucid dreaming" -a type of dreaming in which the person has control over his/her dreams- but that requires practice and a more alert conscious mind while sleeping. It is the conscious part in the dreamer that says: "I am asleep and I am dreaming, so I can do whatever I feel like". And the person keeps dreaming. The kind of control that we do have, when confronted with a dream or a hallucination is the way in which we respond to it. We can be scared, happy, uncertain and curious, once we realize that we have arrived in Fairy Land.


Hallucinogenic substances are chemicals that -once introduced into the body and absorbed by one's systems- will cause hallucinations. The most common hallucinogenic drug is marijuana, but its effects are somewhat subtler than all other substances classified under the same name. For this reason, marijuana will be discussed separately in a following section. The use of hallucinogens is widely spread throughout the world, and goes way back in time, because very powerful hallucinogenic chemicals can be found in plants and fungi, and then synthesized to an even more powerful concentrate. When individuals take these substances, their experiencing of hallucinations is seen as a positive endeavor, in search for the self, the cosmos or fun. But, if we take in example an imaginary person, called "Samuel" and give him some hallucinogen while he is not aware of being administered the drug, his experience will be unpleasant and frightening. Being used to a mind which will correctly "read" the world around him, Samuel will be scared by what he feels and sees, his own emotional turmoil will cause more uneasiness ... because he can't imagine what is going on with him. When -in the 1950's- the CIA put some acid in a person's coffee, the person ended up killing himself. This is to say that when the hallucinations are actively sought by an individual, they will not be seen as negative (they can still elicit a scared response).


Drug-induced states can be compared to many other conscious states that also differ from dreaming. In a way, we are "seeing" things that are not there when we imagine something, remember an event from the past, and we will hallucinate if we have had an epileptic seizure in our temporal lobes or have gone for a long time without sleeping. The drug-induced hallucinations are richer and more often visual in nature than other kinds of mental imagery, but the effect of these substances is not easily predictable because it varies from user to user. The outcome of a "trip" -the name for a hallucinogenic experience- is not predictable because so many external and internal factors influence the individual's experience. Because hallucinations are sensory deceptions, they are private and subjective experiences. No two people will see the same yellow whale floating in the air at the same time ... because there is no whale to be seen, it's in the beholder's mind. It originates from within. How do we tell whether we might be hallucinating or imagining something? Mental imagery is easy to distinguish because of its context and the feelings it carries along. We know the things we imagine are not realistic in nature, so they do not scare us away or make us feel that we cannot get out of where we are. Remembering is also easily distinguishable, because while we remember something, we are in control, actively seeking those images in our mind.


Hallucinogens are defined as chemicals that alter thoughts, feelings and perceptions. Because the mind is the product of a complex inter-relation of neurotransmitters and other chemicals within the brain -and hallucinatory experiences are so personal yet powerful- hallucinogenic substances have been given many different names. These describe their effect on the human organism, but also express a certain attitude towards the drug -a particular ideology in relation to its use and distribution, changing from times to times and culture to culture. In the United States, some other names for these substances are:

Phantasticants- because of the inebriating stimulation that these drugs have, along with their importance to research and science.

Psychedelics- meaning "mind-manifesting".

Psychotomimetic- because these drugs are seen as causing experiences very similar to those of people with psychotic symptoms.

Psychotogenic- as in "generating, causing psychosis".

Whereas in some cultures hallucinogenic substances are accepted as part of religious or spiritual life, the same cannot be said for the United States. When we keep in consideration the potency of these drugs and their possible negative outcomes -such as psychoses and mental impairment on various levels- we can understand why the use of these substances has been condemned. On the other hand, something has to be said for the "glamorizing" publicity that they have received among different generations. Some people have a mind-expanding approach to their use, while among others and more at large, many of these drugs are sold for cheap and taken for simple entertainment. Once again, the state of mind in which a "trip" is experienced is fundamental for its outcome and the welfare of the user.

The reason why hallucinogens are yet to be understood as far as the way in which they affect our mind, is connected to why they can be so dangerous: hallucinogens interact with a wide variety of receptors in the brain and do so very powerfully. It doesn't take a great quantity of a hallucinogen to make it affect our organism, so it's easy to over-dose in the sense of taking too much and being overwhelmed by the experience. Hallucinogenic drugs can be distinguished by the type of effects that they produce, or classified according to their chemical formulas. When we consider their chemical make-up, we have four main groups, and these are derivatives of: 1) phenilethylamine 2) tryptamine 3) lysergic acid 4) cannabinols. In general, hallucinogens of group 1 and 2 are methylated derivatives of the brain neurotransmitters dopamine (DA) and serotonin. The mechanism of action of different hallucinogens has been studied for the past 30 years, and much is yet there to discover. Serotonin (5-HT), dopamine (DA), histamine, and adrenergic receptors have been implicated in the functioning of these drugs. Some examples of commonly used hallucinogens are: LSD and Psylocibin-containing mushrooms. Because we are investigating the effect of drugs that interact with dopamine systems, it's important to consider what dopamine does in normal functioning. The presence of dopamine in the brain was discovered in the 1950's, when the development of new technologies made it possible. Cells using the neurotransmitter DA are located mainly in the midbrain (figure 1) and connect to other areas because their function is to modulate brain activity.

The presence of dopamine in places such as the "nucleus accumbens" is related to addiction. Dopamine reinforces behaviors, and that is why it irrigates the brain with the occurrence of behaviors such as eating, drinking, smoking and it stimulates "pleasure centers" that will say: "That was fun, let's do it again!". Dopamine is part of a larger family of chemicals, called "catecholamines", and the 3 neurotransmitters that belong to this family (dopamine, norepinephrine, epinephrine) are all synthesized from the same enzyme, called tyrosine. The process, very simplified, is the following: tyrosine is transformed into L-DOPA and then L-DOPA keeps transforming and refining itself into dopamine then norepinephrine and -at last- epinephrine. Catecholamines impact emotional states. Dopamine is constantly regulating brain activities because once it's been in a synapse it is then reabsorbed into the sending cell to be used again. This process is called reuptake, and it tell us that DA needs to be taken out of circulation after it's been used because increased levels of it in the brain are related to increased stimulation, and low levels of the same are related to depression. The brain tries to keep an equilibrium by regulating the amount of DA that gets around.


The incredible variety of emotional states that can take hold of a person while under the influence of hallucinogens is due to the interaction of the drug with DA. For example, LSD is a mixed agonist/antagonist at dopamine receptors of the central nervous system (CNS). It has been suggested that it is the class of mixed agonists/antagonists that produce psychotic reactions. LSD affects serotonergic systems as well (5-HT), so that the psychotic effects of LSD are linked to its abilities of linking at the same time with both DA and 5-HT receptors.

We try to understand hallucinogens by paralleling the experience of a "trip" to that of a dream, because the two states of mind share similar qualities and neurotransmitters involved. As yet, we do not know the purpose of dreaming, but we know that when someone is deprived of sleep for too long, he/she will start hallucinating. Some scientists believe that hallucinations involve the role of the brain stem (figure) because this brain structure is involved in arousal, wakefulness and dreaming. Another theory holds that cortical functioning must be altered, so that the person loses ability for appropriate perception and reality testing. Hallucinogens cause experiences that are very similar to those of people affected by schizophrenia. This comparison is useful because it allows us to observe the kind of role that dopamine plays in both situations.

Research has shown that repeated dosages of amphetamine (which means more dopamine in the brain) will produce a psychotic-like set of events in normal people. Also, chemicals that block dopamine receptors in the brain are very good anti-psychotic agents for people with schizophrenia. We can thus conclude that the increase of stimulation caused by more dopamine can result in hallucinations. In some way, hallucinogenic substances must increase the release of dopamine or slow down its reuptake, thus keeping the brain irrigated with the chemical. While "tripping", the context of a situation no longer predicts the relationship of parts to the whole, that is also why a hallucination will very easily evoke an emotional response just as if it were real. Whether or not the observing ego keeps touch with reality may be crucial to the outcome of a trip, because hallucinogens will cause a heightened sense of awareness but will also diminish the person's cognitive abilities. This is why the outcome of a "trip" is influenced by setting and personal expectations: there can be a point in the experience where the person has a hard time distinguishing danger from safety, happiness from disappointment. Just like in a dream, the person that is using hallucinogens will experience incredible arousal (dopamine activity, among other factors) with low external stimulation. The question is: what is it that keeps dreams from occurring in our wakeful state? The dream-like quality of a "trip" and its mystical or magical undertones are possibly what made the use of hallucinogens wide-spread throughout the history of man. It's an experience unlike others, and it also poses some serious dangers to an organism predisposed to certain psychoses or simply too weak to undertake all the stimulation that will take place.


The most common hallucinogen in use is marijuana, derived from the Indian hemp plant (drugs across the spectrum). Three kinds are more commonly grown: Cannabis Sativa -with a tall and woody stem that can grow up to 18 feet-, Cannabis Indica -whose stem only grows up to 2 or 3 feet-, and Cannabis Ruderalis, in Northern Europe and Asia, with a short growing season and low potency. Marijuana is more commonly smoked, but it can also be ingested and in that case its effects will be less potent but last longer. When smoked, its absorbed into the bloodstream through the lungs, and because it is fat-soluble, its "metabolites" remain in the body for a long time. A metabolite is to a chemical like a popsicle stick is to the popsicle. We eat the popsicle because we use the stick to hold on to it, so the stick is an important part of the process. Then, when the popsicle has been all eaten, we are left with the stick, which we can no longer use, and no longer need. We can throw it in a wastebasket, and our friend will know we ate a popsicle because the stick is there. Traces of marijuana consumption can be detected in fatty tissue up to 2 or 3 weeks after someone actually used some.

There are more than 400 chemicals in the marijuana plant, 60 of which can only be found in marijuana and nowhere else -and are therefore called "cannabinoids" (drugs across the spectrum). The main chemical which affects the user's mind (therefore called "psychoactive") is delta-9-tetrahydrocannabinol, for short THC. THC directly affects certain chemical pathways in the brain, but its action is not completely understood because it is believed that THC directly affects many other chemical pathways, and less is known about this aspect of its functioning. Marijuana affects the neurotransmitters ACh (involved in muscular movement and memory), norepinephrine and dopamine. Because its action on dopamine is very strong, smoking marijuana causes changes in mood and perception, and can also interfere with the sleep cycle by upsetting REM sleep in particular. As previously said, there are many similarities between dreaming and hallucinating, so that marijuana's interference with dreaming might be related to its hallucinogenic properties. Some marijuana users report having more dreams after quitting for some time. (drugs and society).

The action of THC upon dopaminergic neurons (neurons that give out dopamine and are affected by it) is very complex. Devane et al. (1988 in Kalat, 1995) found a specific receptor for cannabinoids, a chemical gate that, like a faucet, becomes active when it comes in contact with cannabinoids. These kinds of receptors are found in the hippocampus, basal ganglia and cerebellum, and are among the most numerous in the brain. THC inhibits dopamine reuptake and increases the release and production of dopamine before it's sent into the synapse (Chen at al., 1993). It also increases dopamine and dopamine metabolite levels in the rat's nucleus accumbens (Chen at al., 1990). We know that the nucleus accumbens is involved in reward, and reinforces behaviors that are both good and bad for the person or animal. Behaviors like eating and sexual activity release dopamine in the nucleus accumbens, and the release of dopamine in this specific part of the brain is felt as pleasurable and desirable ... the behavior that caused it will happen again. The same can be said of marijuana consumption. The effect of THC on dopamine-containing neurons is characterized by an increase in the levels of dopamine in various brain areas other than the nucleus accumbens, and the effects of THC are probably mediated by other neurotransmitters other than dopamine (Navarro et al., 1993).

An individual's use of marijuana is very different from the consumption of other hallucinogens, such as LSD, for example. The hallucinogenic properties of THC are somewhat subtler, and we know that a much smaller dosage of LSD will have much more powerful changes on the person's mood and perceptions. A great amount of dopamine in the brain is associated with hallucinations, and many studies have attempted to define the relationship of marijuana to psychosis (events in which the person hallucinates, is delusional, and is affected by mood changes and abnormal behaviors). The association between cannabis use and psychotic episodes can be divided into six possible relationships (Thornicroft, 1990) and these are the following: 1) cannabis use may induce a psychotic episode 2) cannabis use may reveal a latent psychosis (in somebody predisposed to have one) 3) may cause a relapse in the existent psychosis (triggering a psychotic event in someone who had been freed from it for a while) 4) an existing mental disorder might induce the person to use cannabis 5) the relationship of cannabis use and psychosis is ambiguous but present 6) cannabis use has no relationship to psychosis. While keeping all these possibilities in mind, it's important to note that no casual relationship can be drawn, that is, we cannot say with certainty that cannabis use causes psychotic reactions. There are, however, two mental disorders related to cannabis use: cannabis intoxication and cannabis delusional disorder. Cannabis intoxication refers to a temporary state of confusion and emotional turmoil which occurs upon the use of marijuana, but it's generally easily overcome.

Cannabis-induced delusional disorders are rare in the United States but more common in India and Egypt, where cannabis is prepared and boiled down to mixtures that have more powerful dosages and effects. People affected by this disorder show marked improvement only one week after being reported to a clinic. No medication is usually given in toxic psychosis, although some physicians might use antipsychotics, antidepressants and electro-shock therapy, depending on how severe and long-lasting the psychosis seems to be. The interaction of marijuana with other hallucinogens is seen as potentiating the hallucinogenic effect of the latter. An effect known as "flashback" can also occur, in which the cannabis user will re-experience a previous hallucination following marijuana use. This is proof that both LSD and marijuana stimulate some of the same systems in the brain.

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